What's the state of the art for low-latency audio interfaces for DIY projects?

[Surgo]

I'm trying to put together a project that's basically a custom multi-FX unit in an amp head form factor (and, like an amp head, has a power amp part). Basically it'll be a computer in a box, run Reaper on startup, and be controlled through MIDI switches on the front and back.

Raspberry Pi has pisound which looks really great and low-latency, but (1) RPI is unobtanium right now and (2) x86 boards generally offer a lot more raw power. So I'd rather use something x86-based if I can. I've had some trouble figuring out what sort of low-latency hardware is available for the job though. General USB audio interfaces don't really have great RTL without going into the thousand+ dollar range. It seems hard to match to what pisound can do, or embedded ADCs are capable of. Is there anything out there that comes as a board I can use directly for the job here?

[FranklyFlawless]

It seems hard to match to what pisound can do, or embedded ADCs are capable of. Is there anything out there that comes as a board I can use directly for the job here?

Maybe the Teensy, or the Arduino hardware. I know many audio-related projects that use these two, but not for an audio interface, mostly because they are not very relevant to me.

[whyterabbyt]

It seems hard to match to what pisound can do, or embedded ADCs are capable of. Is there anything out there that comes as a board I can use directly for the job here?

Maybe the Teensy, or the Arduino hardware. I know many audio-related projects that use these two, but not for an audio interface, mostly because they are not very relevant to me.

Are you suggesting they'll be able to run Reaper on an arduino or teensy?

Or that they can somehow turn an Arduino or Teensy into an audio interface for a pi?

[whyterabbyt]

Anyway, I'd suggest to the OP that if they're looking for a commercial USB interface for that x86 box (that they're going to run Reaper on), then they're probably best googling for 'lowest latency cheap usb soundcard' and similar. Ive come across multiple comparison lists, including some specifically for guitarists, so probably relevant.

[sjm]

You definitely do not need to spend thousands of bucks to get low latency USB intefaces. I picked up a 17 EUR second hand m-audio Oxygen (that's a 25-key controller with in-built audio interface, including line and XLR) and it was perfectly capable of operating at the lower limits of the ASIO range. Perfectly fine for recording and live playing. I used it as my studio for maybe 6 months while all my other gear was still in boxes after moving.

There are definitely *some* interfaces out there that are less than stellar, and some that fob you off with ASIO4All rather than having their own dedicated drivers, but absolutely no need to spend thousands.

Things get hairier with massive projects and all that, but this really doesn't sound like that's the use case here. Not sure if you're planning on going Linux - if you are, definitely make sure you search accordingly. As you can tell from me mentioning ASIO, my experience is with Windows.

[jupiter8]

Some random thoughts that might or might not be helpful.

There's PI alternatives with even faster processors that are readily availble. OrangePi 5b for example, there are others. They should in theory be compatible with the pisound but i don't know that for certain. Compability has been a bit sketchy but it's getting better. It's mostly GPU acceleration of web browsers and stuff like that. I2S is I2S one would think.

Or just wait for the RPI to be available again. Some claim the chipshortage is over and we're heading in the other direction. The RPI's are suspisciously absent though, so there's that.

[jupiter8]

Forgot half of what i was thinking.

How low latency do you actually need? Sure sub-milliseconds is sexy but do you really need it? In my experience below 10 ms or so is more than adequate.

x86 SOC's also comes with RPI compatible GPIO pins so they should too be compatible with RPI shields. In theory.

I tried the other day running a DAW (because reasons) on the built in Windows drivers (Wasapi) and didn't immediatly notice any latency. Could be you could just run the built in audio jacks without a problem (if it has them).

[robgxmn]

How low latency do you actually need? Sure sub-milliseconds is sexy but do you really need it? In my experience below 10 ms or so is more than adequate.

This is an excellent reminder. Keep in mind 1ms is roughly the equivalent of standing another foot (.3 meter) from the speaker, in terms of latency. I can round-trip outboard gear->DAW->speakers live using 256 sample buffer at 48kHz, which comes to ~5.3ms latency and don't notice the difference vs just plugging the gear straight into the speakers. With 128 samples, ~2.7ms latency, I can do outboard gear->DAW (to record dry and/or wet from VST) -> outboard gear -> DAW again (to record wet from hardware)->speakers, and it's still fine. I don't even remember how much better my interface can do, because I never need it.

Things have come a long way since the USB2 days!

When evaluating choices, you might need to pay attention to both input and output latency, and whether it's affected by recording multiple channels.

[jsalsburg]

Aliexpress X Air XR18 for less than $300.
behringer UMC202HD Audiophile 2x2, 24-Bit/192 kHz USB Audio Interface, $110.